Cathodic Arc Physical Vapor Deposition processes (CAPVD) for applying coatings to a surface of a work piece are now well known. CAPVD is also known as ion plasma deposition, as described in U.S. Pat. No. 6,797,335, the complete disclosure of which is incorporated herein by reference.
The CAPVD process is generally conducted by striking an arc against the surface of a metallic cathodic target material that vaporizes material from the surface. The vaporized material is released in the form of highly ionized plasma (atoms) that can react with a gas on a work piece to form a coating. An example is titanium (vaporized from the metallic cathodic material) and nitrogen (the gas) to form a titanium nitride (TiN) coating on the work piece. Another example is aluminum-titanium-nitride (AlTiN or TiAlN). These coatings are very hard and highly resistant to erosion.
An example of a CAPVD process is the Sablev type cathodic arc source which comprises a short cylindrical shape electrical conductive target at the cathodic material with one open end, which is shown in FIG. 1 [Prior Art]. The anode for the apparatus can be either the vacuum chamber wall or a discrete anode. Arc spots are generated by mechanical trigger (or igniter) striking an open end of the cathodic material making a temporarily short circuit between the cathodic material and anode. After the arc spots have been generated they can be steered in defined areas of the cathode or move randomly over the cathode surface depending on the nature and orientation of the magnetic field around or near the cathode material.
The conditions of the CAPVD process can sometimes be such that un-reacted metal from the cathodic material can form metal particles in the coating that are referred to as macroparticles. The presence of these macroparticles is considered a structural defect in the coating, and can lead to cracks and fissures that weaken the coating. Thus, CAPVD processes are optimized to avoid the formation of these macroparticles or filters are used to remove them. An example of a CAPVD process that uses such a filter is the Aksenov quarter-torus duct macroparticle filter, shown in FIG. 2 [Prior Art], which consists of a quarter-torus duct bent at 90 degrees from the arc source and the plasma is guided out of the duct by principle of plasma optics, whereas the macroparticles continue on a straight path unaffected by the magnetic fields of the duct.